Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.81	9.504%	$193.614	$193.61	$193.60	$193.60
Purchase #2	$121.85	4.661%	$127.5294	$127.53	$127.55	$127.50
Purchase #3	$136.25	5.824%	$144.1852	$144.19	$144.20	$144.20
Purchase #4	$214.98	10.215%	$236.9402	$236.94	$236.95	$236.90
Purchase #5	$63.89	5.547%	$67.434	$67.43	$67.45	$67.40
Purchase #6	$129.52	11.217%	$144.0483	$144.05	$144.05	$144.00
Purchase #7	$86.30	5.751%	$91.2631	$91.26	$91.25	$91.30
7 purchase totals =	$929.60		$1,005.0142	$1,005.01	$1,005.05	$1,004.90